Sorbent for removal of heavy metals

ABSTRACT

A novel use for sorbents involving the removal of heavy metals from liquid solutions has been discovered. More specifically, it has been discovered that these sorbents remove alkyl lead moieties from gasoline. The sorbents are comprised by a suitable substrate bonded to a metal by means of organic or inorganic exchanger functional groups.

Umted States Patent 1 [1|] 3, Whitehurst Nov. ll. 1975 1 SORBENT FORREMOVAL OF HEAVY 2.392.846 l/lJ-th Friedman... Zusflit R METALS 3105188WW6} A \crs....,.,..... lUH/Zil R 3.785.968 H1974 Whitchurst 108325] Rlm'cflwri Darrell Duayne Whilehursh 3.791.968 2/1974 Whitchurst t: 1zumil R TltuSVlllC. NJ. 3.793.185 2/1974 Whitehurst ct ul ll h'llil R3.799.871) J 974 H "l "l Illfifll'l R [73] Asslgnec: MobllOllCorporatlonH [22] Filed: Feb. 21, I974 Fri/nary E.\LUH1H('I'DClbfil't E. Guntz.-ls.sr'.smm l;'.\'umim'r luzmitu M. Nelson [21] Appl' 444609 Attorney.Agent. or F1'rmAndre\\ L. (.lulmriuult Related .8. Application Data {63](nntmuullun 0t Scr. Nu. H9164. Dec. 2). I972. [57] ABSTRACT hmdmml Anow] use for sorhcnts intuhing the rumuutl 0t heavy metals from li UlLlSOlUIlOHS has been dixcu J I 1 7 '1 a q 208/251? Avg/-53? cred. Morespecifically. It has been LllSLU\Cl"Ctl that l-f'l l g 7/00 thesesorhcnts rcmuvc ttlk \l lend nlUlQllCS from gll$tl- Fleld 593ml! 308/25]line. The sorhcnts are comprised h :1 suitable sul 208/297. 29 strutshontlctl to a metal] b means of org'tmic or inurganic cation exchangerfunctional groups. [56] References Cited UNITED STATES PATENTS IWWHZUX/ZSI R Pursnns.

5 Claims. 4 Drawing Figures U.S. Patent Nov.1l, 1975 Sheetlof2 3,919,077

U.S. Patent Nov. 11,1975 Sheet 2 of2 3,919,077

FIGURE 4 0o @4250! Lo .0

90 Q Absorbonce 9 .016 1 A ZTronsminonce g m .8 o 7 I z m U E 8 .I25 3I6 x 8. 2 m o m a E .s g s a: rn I, .4 g .3 5. '2 n2 .5 g

l l I I I I I0 20 3O 4O 5O 6O 7O 8O 90 I00 I. Pb REMOVAL SORBENT FORREMOVAL OF HEAVY METALS CROSS-REFERENCE TO RELATED APPLICATION This caseis a continuation of U.S. Pat. application Ser. No. 319,264 filed Dec.29. 1972 now abandoned.

BACKGROUND OF THE INVENTION 1. Field of the Invention The inventiondeals with the removal of metals from compositions containing suchmetals as organic or inorganic compounds. it more particularly refers tore moval of lead from gasoline. The need for the removal of metals isevidenced by the fact that their presence in hydrocarbon charge stocksconducted to catalytic cracking and catalytic reforming process units isknown to poison and shorten the life of the catalyst with which suchmetal contaminated stocks come into contact.

It is also desirable to remove trace metals from lubri eating oils or torecover soluble metal catalysts from reactor effluents or polymersolutions. The removal of heavy metals such as mercury, silver, calciumand the like from the water effluents of chemical or photo graphicplants is also highly desired from an ecological standpoint.

Unbumed hydrocarbon, carbon and carbon monoxide emissions are regardedby many as representing a substantial source of air pollution. Theseengine emissions are subject to photo-chemical reaction in theatmosphere, providing what has been termed smog. which is an irritant oflachrymal and respiratory system tissues.

The incompletely oxidized carbon. e.g. carbon monoxide and unburnedhydrocarbons, present in engine exhaust are the result of incompletecombustion of the hydrocarbon fuel in the engine combustion chamber.Complete oxidization of such carbon monoxide and/or hydrocarbonstransforms such to carbon dioxide and water, probably in the form ofsteam due to the high combustion temperature. Neither carbon dioxide norsteam is considered a harmful emission.

Various means have been employed to reduce or eliminate carbon monoxideand unburned hydrocarbon emissions. One approach has been to pass theconbustible exhaust through a catalytic converter located in theengine's exhaust system where the carbon monoxide and hydrocarbons arecatalytically oxidized, usually by the introduction of supplemental air,to carbon dioxide and water.

It is known that residues of alkyl lead from combustion of leadedgasoline tend to poison catalysts available for oxidizing unburnedhydrocarbons and carbon monoxide in an engine exhaust. Such poisoningseverely shortens the useful life of exhaust combustion catalysts. Ithas thus been heretofore proposed that lead free" gasoline be suppliedfor use in automobiles equipped with emission control devices whichutilize catalysts to help further oxidize exhaust gases.

Under most proposals. small. trace amounts of lead would be allowed in"lead-free gasoline. The Federal Government regulations require allgasoline sales outlets to furnish at least one grade of gasoline havingless than 0.07 gram of lead per gallon to the public by July 1. I974. OnFeb. 23, i972 the Environmental Protection Agency in a paper relating tothe l970 Clean Air Act Amendments offered for comment a requirement of0.05 grams of lead per gallon of gasoline. Other proposals have beeneven more stringent.

The normal network of petroleum product distribution involves railroadtank cars. pipelines. water borne tankers, tank trucks and bulk storagetanks. For commercial operation these are presently set up to handledifferent products. For example. the same pipeline might be used toconvey a shipment of regular grade gasoline. premium grade gasoline.distillate fuel and other light liquid products in succession. Accordingto present procedures. that portion of the fluids carried by thepipeline which constitutes an intermingling of the two products at theirinterface is diverted to use with the lower grade product. thus avoidingdegradation of the higher grade hydrocarbon.

However when leaded gasoline is followed by leadfree gasoline, not justthe interface comprising in intermingling or the two products. but theentire leadfree shipment becomes degraded. When leaded gasoline.containing tetraethyl lead. tetrumethyl lead or a mix ture oftransalkylation products of the two is contacted with the metal or othersurfaces of transportation and storage facilities, a significant amountof lead is left deposited in scale and on these surfaces. Since alkyllead components are infinitely soluble in light hydrocarbons such asgasoline. upon after using the same faculties for lead free gasoline.the latter product becomes contaminated with lead which may run as highas about 0.l grams of lead per gallon or more. These amounts of lead aresufficient to impair the life of exhaust emission control oxidationcatalysts and are in excess of the presently proposed allowable limitson lead content of lead free gasolines.

2. Description of the Prior Art Techniques have heretofore been knownfor removal of dissolved or suspended heavy metal contaminants fromliquid products.

In catalytic cracking and reforming operations, the use of guardchambers containing a variety of sorbents and/or catalysts intended toremove heavy metal contaminants from the charge stock before contact ismade with the catalyst have been described. Catalytichydrodesulfurization processes and catalysts remove some amount of heavymetal contamination from hydrocarbon streams processed thereby.

Systems for removal of lead from gasoline have also been proposed.Presently known techniques require considerable time or arenon-selective in effecting removal from the gasoline not only of thelead but also of those additives which are desired to be retained. suchas antioxidants. anti-icing additives. metal passivators, detergents andthe like.

One previously proposed system for removing lead from gasoline isdescribed in US. Pat. No. 2.368.26l. There. acid activated clay. such asbentonite which had been previously treated with hydrochloric orsulfuric acid. is used. Leaded gasoline is percolated through the claywhereby up to percent of the lead present is removed. Unfortunately,acid activated clays will also remove other gasoline additives which arerequired or desired for proper protection and functioning of automotiveequipment.

Another approach is that described in US. Pat. No. 2,392,846. Accordingto an example in this patent. a five gallon lot of leaded gasoline istreated with 20 ml. of stannic chloride followed by addition of grams ofactivated carbon. This results in decomposition of the tetraalkyl leadand adsorption of the lead decomposition products on the activatedcarbon thus drastically reducing the lead content. The gasoline isremoved from the activated carbon by decantation. This is a very slowprocess which permits the processing of about 35 gallons of gasoline perhour. Unfortunately even in this system, the additives desired to beretained in the gasoline are also adsorbed by the activated carbon.

Both the processes described in the cited prior pa tents depend foreffectiveness on a chemical conver sion of the tetraalkyl lead. The leadcompounds can be reacted with such materials as halogens. halogen acids.metal halides. metal salts. sulfur dioxide. carboxylic acids. metals inthe presence of hydrogen etc. While alkyl leads are infinitely solublein gasoline. the resulting decomposition products are not readilysoluble in hydrocarbons and hence can be selectively adsorbed on highsurface adsorbents.

The American Oil Company. in a paper presented at the May 9. I972meeting of the API Division of Refin ing noted that in a significantnumber of its stations it was presently unable to meet the 0.05gram/gal. or even the 0.07 gram/gal. requirement using scrutinouscontrol of their distribution system and segregation of products. Thearea of greatest potential contamination was that of the service stationitself. The report would indicate that gasoline manufacturers withdistribution systems more extensive than those of American. and relyingonly on distribution control to ensure that the unleaded gasoline willremain within specifications. face an extremely difficult and expensiveundertaking.

It is a primary objective of this invention to provide means to removeheavy metals from liquid, particularly hydrocarbon, streams. It is afurther objective of this invention to remove lead alkyls from gasoline.Other and additional objects of this invention will become apparent froma consideration of this entire specification including the claims anddrawings.

SUMMARY OF THE INVENTION In accordance with and in fulfillment of theaforestated objectives. an embodiment of this invention consists ofutilizing a sorbent comprising a porous solid substrate having poreswith a minimum pore diameter of about IDA. and a minimum surface area ofabout mlg; the substrate being modified by a functional group of anorganic or inorganic cation exchanger which acts as a bridging memberbetween the substrate and a metal; the metal being a Group lB. H8 or IVAmetal having an atomic number of at least 29 for the removal of heavymetals from non-aqueous liquid solutions. and more particularly forremoving lead from gasoline. For purposes of this dislosure. the groupdesignations referred to are as defined in Lange's Handbook of Chemistryat 58-61 (10th ed. 1967), the term cation exchanger" is defined in [anExchange by F. Helfferich at 12-47 (1962).

The following metals work particularly well: copper (Cu). silver (Ag),mercury (Hg) and tin (Sn).

BRIEF DESCRIPTION OF THE DRWINGS FIG. 1 of the drawings attached heretorepresents a typical service station gasoline pump modified according tothe present invention.

FIG. 2 is an enlarged view of the cartridge for containing the leadremoval agent.

FIG. 3 is a view in fragmentary section of a cartridge for containingthe lead removal agent.

FIG. 4 is an analytical curve illustrating amount of lead removal as afunction of absorbance and transmittance.

DESCRIPTION OF SPECIFIC EMBODIMENTS In a preferred embodiment. thesorbent is placed in a canister in the discharge hose of a servicestation gas oline pump. This preferred embodiment is more particularlydescribed by making reference to FIGS. 1-3.

As shown in FIG. I. a gasoline dispensing pump of conventional designincludes a housing indicated generally at 10 within which are containeda motor driven pump and a metering device. not shown. The meteringdevice drives, through suitable gearing. indicators within a panel ll toreport gasoline dispensed and price for the amount so dispensed. Thefuel after passing through the metering device. is conducted to theoutside of the housing through a pipe connection 12 and into a dischargehose l3 equipped with a valve nozzle I4.

The modification to conventional dispensing pumps is a canister 15connected to the fuel discharge 12 by a pipe 16 provided with a valvefor which the operating handle is shown at 17. Fuel from the pipe 16 isconducted to the top of canister 15 containing the lead removal agentfrom which it passes through a suitably prepared cartridge and is thencedischarged to hose I3 and nozzle 14.

A typical cartridge is shown in FIG. 3 as constituted by a gauzecontainer 18 within a wire mesh supporting cage 19. Disposed within thecontainer gauze I8 is a mass of the lead removal agent of the type whichcharacterizes this invention.

For the usual service station, a cartridge having a diameter of about 24inches and length of about 12 inches should be adequate to reduce thelead content to acceptable levels for a working life of about one month.When it is desired to change the cartridge, valve 17 is closed. the hose13 is drained and the canister 15 is removed by unthreading from the topportion thereof. It is thus a simple matter to replace the cartridge ina very short period of time and return the dispensing pump to duty.

As previously noted, this invention is to be utilized in non-aqueoussolutions. as the presence of water limits the performance of thesorbent. Due to the fact that gasoline on occasion contains smallamounts of water. it is contemplated that a deliquescent material may beplaced in the upstream portion of the cartridge to prevent the sorbentfrom being rendered of limited performance due to the presence of water.

EXAMPLES l-ll These tests consisted of contacting approximately three tosix volumes of gasoline containing 2.5 grams of lead/gallon of gasolinewith one volume of sorbent under ambient conditions followed by a leadanalysis of the contacted gasoline.

Following the contacting of the 2.5 grams of lead/gallon of gasolinefuel with the sorbent prepared as previously described, the lead contentof the treated gasoline was analyzed as follows;

A 5 part by volume sample of gasoline was treated with 1 part by volumeof a saturated solution of silver nitrate (AgNo in absolute ethanol.After standing for ten minutes. the content of reduced silver in thesample was determined by turbidometric technique. These measurementswere done at 425 nm or 500 nm depend ing on the gasoline used. Themeasured transmission was compared with a standard analytical curvesimilar to the one illustrated by FIG. 4.

The percent lead removed by the sorbents is given in Table l.

TABLE 1 Sorhent Percent Example desig- Pb rnumber nation Sorbcnt typemoval l AW 62 J C O OCn 2 a v M (H O -s Oz-Na [(lul 3 BK 68 S 03-8 11*-S OrCu -S OrAg tPd") 6 X 81 S 03' S n T a t J5 J -S Oa'I-Ig J S Or(l).1(Ag ).n Zeolite-Xl Ag (Pd 24 Zeolite-X S 11* (Pd 40 Zeolite-X] Ag+ 83Zeolite X is a substrate containing a cation exchanger functional groupand may be chemically defined as a crystalline aluminosilicate having aprescribed crystalline form as described by A. G. Oblad. Oil & GasJournal 70. 84. 1972.

What is claimed is:

l. A method for effecting the removal of heavy metal contaminants fromsolution in a substantially hydrocarbon solvent which comprisescontacting said solution. in a flowing system. with a solid sorbenthaving a surface area of at least about 10 m /g, having pores of atleast about l0 angstroms diameter and comprising a material selectedfrom the group consisting essentially of carboxylic or sulfonic acidsubstituted organic cation exchange resin or a zeolite-X zeolite whichhas bonded thereto through its acid sites a metal of Groups [B "B or lVAof the Periodic Table having an atomic weight of at least 29.

2. The method as claimed in claim 1 wherein said metal is selected fromthe group consisting of Cu, Ag, Hg and Sn.

3. The method as claimed in claim 1 wherein said heavy metalcontaminants are lead alkyl moieties and said substantially hydrocarbonsolution is gasoline. and said contacting is carried out at about 50C.to C. and at space velocities of up to about 40 L'HSV.

4. A method as claimed in claim 3 wherein said sorbent is located in aconduit means in a gasoline distribution system between a storage meansand a dispensing means.

5. A method as claim in claim 4 including pumping said gasoline fromsaid storage means through said con duit means to said dispensing meansand sorbing said lead from said gasoline during said pumping.

1. A METHOD FOR EFFECTING THE REMOVAL OF HEAVY METAL CONTAMINANTS FROMSOLUTION IN A SUBSTQNTIALLY HYDROCARBON SOLVENT WHICH COMPRISESCONTACTING SAID SOLUTION, IN A FLOWING SYSTEM, WITH A SOLED SORBENTHAVING A SURFACE AREA OF AT LEAST ABOUT 10 N2/G, HAVING PORES OF ATLEAST ABOUT 10 ANGSTROMS DIAMETER AND COMPRISING A MATERIAL SELECTEDFROM THE GROUP CONSISTING ESSENTIALLY OF CARBOXYLIC OR SULFONIC ACIDSUBSTITUTED ORGANIC CATION EXCJANG RESIN OR A ZEOLITE-X ZEOLITE WHICHHAS BONDED THERETO THROUGH ITS ACID SITED A METAL OF GROUPS IB, IIB ORIVA OF THE PERIODIC TABLE HAVING AN ATOMEC WEIGHT OF AT LEAST
 29. 2. Themethod as claimed in claim 1 wherein said metal is selected from thegroup consisting of Cu, Ag, Hg and Sn.
 3. The method as claimed in claim1 wherein said heavy metal contaminants are lead alkyl moieties and saidsubstantially hydrocarbon solution is gasOline, and said contacting iscarried out at about -50*C. to 100*C. and at space velocities of up toabout 40 LHSV.
 4. A method as claimed in claim 3 wherein said sorbent islocated in a conduit means in a gasoline distributi system between astorage means and a dispensing means.
 5. A method as claim in claim 4including pumping said gasoline from said storage means through saidconduit means to said dispensing means and sorbing said lead from saidgasoline during said pumping.